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Intel Sandy Bridge RC6 Is Good To Go

02-27-2012, 02:20 AM

Phoronix: Intel Sandy Bridge RC6 Is Good To Go

It looks like the debacle concerning RC6 power-savings support for Intel Sandy Bridge hardware is finally behind us. Intel thinks everything is worked out and ready to be enabled upstream (again) with the next Linux 3.4 kernel cycle and Canonical has enabled RC6 by default in Ubuntu 12.04 LTS. Here are some tests showing the performance benefits and power-saving abilities of using the RC6 hardware feature on Sandy Bridge processors.

Nexuiz was a similar story... The power consumption when running this once-popular open-source first person shooter went up by about 30% (26 Watts to 34 Watts) while the frame-rate performance went up by 22%. The deep/deepest RC6 states still were of no significant benefit.

The deepest RC6 got the same fps as other rc6 enabled states, but at 4W lower power consumption.

Comment

Just to be clear, we can't expect power usage to go down in gaming scenarios, when power management features like RC6 deal with lowering idle/low load power. Gaming is not low load. On Sandy Bridge, extra thermal headroom is converted to Turbo. Turbo can't be at full speeds all the time, but lower idle power will allow greater thermal headroom to enable longer duration in Turbo when needed(not forever of course, within the limits of the timer in the chip).

There's a reason fastest chips usually consume the most power, at load. But if the idle/low load management is good enough, you can make it so for most of usage scenarios, it acts like a lower TDP chip.